In a semiconductor fabrication apparatus, there is a known mechanism such that a plurality of processing chambers is coupled to a transfer chamber having a substrate transfer device, i.e., cluster tools or multi-chamber mechanism. Such a mechanism has some merits that a vacuum processing on a substrate can be performed continuously without breaking a vacuum state in case of performing same several times, for example, and a processing chamber can be kept away from the atmosphere. Further, high throughput can be obtained.
In the cluster tools mentioned above, one side of a polygonal transfer chamber is airtightly coupled to a load-lock chamber, and, at the same time, other sides are airtightly coupled to a plurality of processing chambers. In addition, a substrate transfer device installed inside the transfer chamber has two forks for supporting a semiconductor wafer (hereinafter, referred to as ‘wafer’). Here, the forks can be revolved, extended, and shrunken by operations of a robot.
While, in the cluster tools, one fork of the substrate transfer device reaches to a load-lock chamber to pick up an unprocessed wafer to mounts same thereon, the other fork reaches to load a processed wafer thereon. Thereafter, the unprocessed wafer on the one fork is transferred to the processing chamber by revolving the robot by 180°.
However, if the robot is rotated by 180° whenever a wafer is loaded in one processing chamber, it takes a relatively long time to transfer the wafer. As a result, throughput becomes lowered. For insuring high throughput by effectively using the cluster tools, it is important to transfer the substrate efficiently. As an apparatus for efficiently transferring a substrate, there has been disclosed an apparatus in Japanese Patent Laid-open Publication Heisei No. 11-207666.
In a cluster tools described in the aforementioned prior art, as shown in FIG. 21, five processing chamber stations (hereinafter, referred to as ‘processing chamber’) 91 to 95 are airtightly coupled to a transfer chamber 90, and a handling robot 96 for transferring a wafer of a substrate to the transfer chamber 90 is disposed. The handling robot 96 has two transfer tables 97a and 97b for supporting the wafer. The transfer tables 97a and 97b are constructed so as to appear and disappear in the same direction as a revolving direction or in a direction shifted a small angle, by robot link mechanisms 98a and 98b which can conduct extending and shrinking operations, and revolve. Thereby, the transfer tables 97a and 97bneed not to revolve to reach a next processing chamber but revolve by a few angles such that a processed wafer can be exchanged with an unprocessed wafer in the same corresponding processing chamber.
FIGS. 17 to 20 of the aforementioned prior art show operation states of the conventional handling robot mentioned above. In this example, it is described that each of the two robot link mechanisms 98a and 98b stands by in the transfer chamber 90 while supporting an unprocessed wafer. At first, a wafer of a first robot link mechanism 98a is loaded into a processing chamber 93, and subsequently, a wafer of a second robot link mechanism 98b is loaded into the processing chamber 94 adjacent to the processing chamber 93.
However, when comparing the time required for performing a process in each processing chamber of the cluster tools with that for transferring an unprocessed wafer from a load-lock chamber to the processing chamber, there are cases that the processing time is shorter than the transfer time and vice versa. Here, in case where the processing time is longer than the transfer time, as described in the prior art, the unprocessed wafer is held by the substrate transfer device in the transfer chamber until performing a process on a prior wafer is completed in the processing chamber. Upon completing the process in the corresponding processing chamber, the processed wafer will be immediately unloaded. Since the processed wafer and an unprocessed wafer can be quickly exchanged in the corresponding process chamber, it is possible to reduce the transfer time and transfer effectively.
However, in case where the processing time is shorter than the transfer time, the processing on the wafer must already have been completed in the processing chamber while the unprocessed wafer being transferred from the load-lock chamber by the substrate transfer device. Thus, the configuration of the aforementioned prior art does not help to facilitate the transfer of the wafer effectively since there is no case where the unprocessed wafer stands by until performing a process on a prior wafer is completed in the processing chamber, in such a state where a wafer is supported by the substrate transfer device in the transfer chamber.
Further, there are the following problems in an apparatus for performing a vacuum process of a cluster tools or the like. For example, when supporting or repairing the apparatus, an interior of the processing chamber is opened to the atmosphere by opening a lid of the processing chamber. At this time, particles from the outside are introduced into the processing chamber to thereby be attached thereto. In addition, reaction products are attached to the processing chamber on performing a vacuum process, e.g., etching. Meanwhile, when loading a wafer from the load-lock chamber into the processing chamber, a gate valve of a sluice valve is opened. At this time, if there is a pressure difference between the processing chamber and the load-lock chamber, shock waves are generated to thereby peel off the particles attached to the chamber. As a result, there is a concern for contaminating the wafer.
Meanwhile, there has been known a technology for suppressing a rapid flow of a gas and preventing an oscillation by setting up the pressures of two chambers at the vicinity of the atmosphere so as to minimize the pressure difference before opening the gate valve between the processing chamber and the load-lock chamber or the processing chambers adjacent to each other, and making the pressures equal by opening a connecting line valve (Japanese Patent Laid-open Publication Heisei No. 6-177060).
However, the aforementioned method is not effective since shock waves are generated when opening the valve in the case of employing a connecting line between the vacuum chambers. Further, even if the pressure difference becomes small, the shock wave strong enough to peel off the particles inside the chamber may be generated depending on a pressure band. Since a design rule of a semiconductor device is getting more and more strict, it is required that the substrate should be managed more carefully to prevent the contamination of the wafer due to the particles. However, it is difficult to respond to such needs with the conventional technology.